How to sum two field

[Anonymous]

code type    detail                hourspent

a                      big                 10

a                       small             14

b                       big                11

c                       big                12

d                       medium         12

e                       big                 11

a                         big                 21

What formula to use to sum only for code type=a &detail=big?

[#2]

=sum({<codetype = {'a'}, detail = {'big'}>} hourspent)